Research On Portable Laser Speckle Contrast Imaging System And Its Applications

Monitoring the change of blood flow in real time is crutial for studying the functional activities of biological tissue, the mechanism of disease, the diagnosis and the intraoperative imaging. It is necessary to develop the embedded medical device with the feature of small size, easy to use and special function during the clinical diagnosis and treatment. At present, somel methods used to measure blood flow has the disadvantages of low spatial-temporal resolution or the injection of exogenous substances. As a noninvasive full-field technique without the need of scanning, laser speckle contrast imaging has been widely used to study blood flow with high spatial and temporal resolution in real time. However, the structures of conventional laser speckle contrast imaging systems are all based on personal computers for image processing with large size, which potentially limit the widespread clinical utility. Seed vigour testing plays an important role to guide the work in agricultural production. However, current methods used to test seed vigour suffer from the long testing period and can not test outside.In order to solve these problems, a portable laser speckle contrast imaging system is constructed in this thesis. The multimedia digital video processor is adopted as the core of the system to provides the highspeed calculation with laser speckle spatial contrast analysis algorithm and laser speckle temporal contrast analysis algorithm. To enhance the flexibility, the system support several input and output devices of image. In order to have friendly user interface, the system adopts the graphical user interfaces. We also developed the laser speckle spatial contrast analysis algorithm which was efficient for Digital Signal Processor implementation. The experiment results demonstrated a display frame rate of 25 frames per second for blood flow images, and the resolution of 640×480 pixels was achieved in the high level of integration system. Flow phantom experiment showed that the measurement velocity and actual velocity had a linear relationship with correlation coefficient of 0.9597, demonstrating the validity of the portable system. We also compared the difference caused by the different velocity calculation equations and different data types in computation. In vivo experiment shows that the mean value of relative difference image is 3.69×10-3 by using approximation method. The system is applied on monitoring cerebral blood flow of rat under carotid artery occlusion test and skin blood perfusion test. Compared with the commercial laser speckle contrast imaging system, the portable laser speckle contrast imaging system with the feature of small size and video frame rate is suitable for the application in clinical diagnosis.In addition, the portable laser speckle contrast imaging system is applied to test seed vigour. The result of the soaked corn seed test demonstrated that Fujii method have the highest contrast between embyro and endosperm. The shorter of the inter-frame space the higher of the contrast. The contrast is 0.52 when the inter-frame space of CCD camera is 100 ms. The results of the system are the same as in TTC staining, which shows that the system can be used for testing the seed vigour.